This invention relates to spark wheels for use in cigarette lighters and the like, and more particularly to a method for manufacturing the abrasive surface for the spark wheel and dies for use in the process.
In order to properly function, a spark wheel must incorporate an abrasive surface which, when rotated against a flint of similar pyrophoric material, will produce a spark to ignite a fuel-fed wick or jet of flammable gas. As is well known in the art, before the abrasive surface can be formed, substantially parallel grooves must be formed in the cylindrical surface of the wheel blank at an acute angle to the sides of the wheel in order to provide the proper offset spacing for the cutting edges of the spark wheel.
The two well-known prior art methods for producing the desired abrasive surface for the spark wheel are chiseling and broaching. The most commonly used prior art process is the chiseling process, in which the grooved spark wheel is rotated while a chiseling tool or blade reciprocatingly cuts into the peripheral surface of the spark wheel as the spark wheel is rotated about its central axis. The chiseling process forms a plurality of substantially linearly arranged inclined teeth in the surface of the spark wheel. This, in combination with the grooves which have been previously cut into the spark wheel surface, produces the required abrasive surface for the spark wheel.
The second known process for producing spark wheels is disclosed in U.S. Pat. No. 2,455,348. As shown therein, the grooved cylindrical wheel is pushed through a broaching die to produce the desired abrasive surface for the spark wheel.
Both of these prior art methods are extremely disadvantageous, due to the expense required to produce an effective spark wheel. Repeated handling of the spark wheel during production is required in both processes, thereby increasing the production costs.